1. Field of the Invention
The present invention relates to an automotive alternator mounted to an automotive vehicle such as a passenger car or a truck, for example, to a stator winding assembly of the automotive alternator, and to a method of manufacture for the stator winding assembly.
2. Description of the Related Art
To reduce the size and increase the output of alternators driven by internal combustion engines, it is necessary to increase the space factor of electrical conductors housed within magnetic circuits of a stator, and to line up and increase the density of crossover portions (coil end portions) of a stator winding, and various improvements have been proposed, as for example in Japanese Patent Laid-Open No. HEI 11-164506.
FIGS. 27 and 28 are perspectives from a front end and a rear end, respectively, of part of a stator winding of a conventional alternator of this type, and FIG. 29 is a perspective showing a construction of a conductor segment used in the stator winding of the conventional alternator shown in FIGS. 27 and 28.
In FIGS. 27 to 29, a stator 90 is constituted by a stator core 91, a stator winding 92 constituted by a number of electrical conductors disposed inside slots 91a formed in the stator core 91, and insulators 93 providing electrical insulation between the stator core 91 and the electrical conductors.
In the stator core 91 of this conventional example, ninety-six slots 91a are disposed at even pitch so as to house two three-phase alternating current windings such that the number of slots housing each phase portion of the three-phase alternating current windings corresponds to the number of magnetic poles in a rotor. Four electrical conductors are housed within each of the slots 91a so as to line up in one row in a radial direction, and these electrical conductors are connected in a predetermined winding pattern to form the stator winding 92. Here, a first position, a second position, a third position, and a fourth position in a radial direction from an inner circumferential side inside the slots 91a in which the electrical conductors are housed will be called a first address, a second address, a third address, and a fourth address, respectively.
Large segments 95 and small segments 96 are formed by bending short lengths of a conductor such as copper into general U shapes in which pairs of straight portions 95a and 96a are linked by turn portions 95b and 96a. The small segments 96 are inserted one at a time from a rear end into pairs of slots 91a six slots apart (a pitch of one magnetic pole). Similarly, the large segments 95 are inserted one at a time from the rear end into pairs of slots 91a six slots apart (a pitch of one magnetic pole). Then, end portions of the large segments 95 and the small segments 96 extending outwards at a front end are joined to each other to constitute the stator winding 92.
More specifically, in pairs of slots 91a six slots apart, the small segments 96 are inserted from the rear end into the second address within first slots 91a and into the third address within second slots 91a, and the large segments 95 are inserted from the rear end into the first address within the first slots 91a and into the fourth address within the second slots 91a. Thus, within each of the slots 91a, two straight portions 95a of the large segments 95 and two straight portions 96a of the small segments 96 are disposed to line up in a row of four in a radial direction.
Then, end portions 95c of the large segments 95 extending outwards at the front end from the first address within the first slots 91a are joined to end portions 96c of the small segments 96 extending outwards at the front end from the second address within the second slots 91a six slots away in a clockwise direction from the first slots 91a. In addition, the end portions 95c of the large segments 95 extending outwards at the front end from the fourth address within the first slots 91a are joined to the end portions 96c of the small segments 96 extending outwards at the front end from the third address within the second slots 91a six slots away in a counter-clockwise direction from the first slots 91a. Thus, two winding sub-portions are formed, which are lap windings having two turns per lap. These two winding sub-portions are connected in series to form one winding phase portion having four turns.
Similarly, a total of six winding phase portions each having four turns are formed by offsetting by one slot at a time the positions of the slots into which the large segments 95 and the small segments 96 are inserted. Then, three each of these winding phase portions are connected into each of the two three-phase alternating current windings which constitute the stator winding 92.
In the conventional stator 90 constructed in this manner, at the rear end of the stator core 91, the turn portions 95b of the large segments 95 are disposed so as to cover outer circumferential sides of the turn portions 96b of the small segments 96 inserted into the same pairs of slots 91a. As a result, the turn portions 95b and 96b are disposed circumferentially to constitute a rear-end coil end group.
At the front end of the stator core 91, on the other hand, joint portions formed by joining the end portions 95c of the large segments 95 extending outwards at the front end from the first address within the first slots 91a and the end portions 96c of the small segments 96 extending outwards at the front end from the second address within the second slots 91a six slots away, and joint portions formed by joining the end portions 95c of the large segments 95 extending outwards at the front end from the fourth address within the first slots 91a and the end portions 96b of the small segments 96 extending outwards at the front end from the third address within the second slots 91a six slots away are disposed to line up radially. As a result, joint portions formed by joining the end portions 95c and 96c to each other are disposed circumferentially in two rows in a radial direction to constitute a front-end coil end group.
Because the stator winding 92 of the conventional alternator is constructed by inserting the large segments 95 and the small segments 96 formed by bending the short lengths of conductor into general U shapes into the slots 91a of the stator core 91 from the rear end and joining together the end portions of the segments extending outwards at the front end as explained above, one problem has been that a large number of the large segments 95 and the small segments 96 must be inserted into the slots 91a of the stator core 91 and end portions thereof must be joined one by one, significantly reducing workability and decreasing mass-producibility.
In addition, in order to join the end portions 95c of the large segments 95 and the end portions 96c of the small segments 96, it is necessary to clamp a portion of each of the end portions 95c and 96c together using a jig, and another problem has been that it is necessary to extend the segments out by an extra amount from the stator coil 91 to allow for the clamping, preventing the stator 90 from being reduced in size.
In the conventional stator 90, because the end portions 95c and 96c are joined to each other by clamping portions thereof in a jig and welding the end portions 95c and 96c together, the height of the coil ends is increased, and the large segments 95 and the small segments 96 are softened by temperature increases during welding, thereby causing rigidity of the stator to be decreased. As a result, other problems have been that when the conventional stator 90 is mounted to an alternator, coil leakage reactance in the coil end portions is increased to cause output to deteriorate, wind resistance is increased to exacerbate wind noise, and rigidity of the stator is reduced to exacerbate magnetic noise.